1. Field of the Invention
The present invention relates to a thin film device in which there is formed an electronic element such as a capacitor or a coil, and to a method for manufacturing such a thin film device.
2. Related Background Art
A thin film device has plural electronic elements in its interior, with a protective resin film being formed on the elements, covering them entirely. A soft resin film and a hard ceramic substrate are sliced simultaneously during separation of plural thin film devices through dicing of the wafer where the thin film devices are formed. In such cases there occur delamination between the resin and the substrate, and gumming of the dicing blade by the protective resin film, all of which detracts from mass productivity. Therefore, a predefined metal layer is coated on the terminal electrodes of the thin film device. Preferably, such terminal electrodes are made to protrude beforehand out of the resin protective film at the stage of thin film device integration on the wafer. Doing so allows slicing the ceramic substrate alone at the stage of thin film device separation, thereby increasing mass productivity while expanding the bonding surface area with outer terminals formed by plating, enhancing thus bonding reliability through a more secure bonding.
Such thin film devices are disclosed in, for instance, Japanese Unexamined Patent Application Laid-open Nos. 2002-33559, 2004-172348 and 2005-109410.
However, delamination between the resin protective film and the terminal electrode body may also occur even when the outer terminals are exposed to the exterior of the resin protective film. As a result of diligent research, the present inventors found that the reason for this lies in the dissolution of metal oxides formed between the underside of the resin protective layer and the top of the terminal electrode body during the step of washing with an acidic solvent, and which eventually gives rise to delamination. Examples of such metal oxides include, for instance, Cu2O, CuO or the like. Such metal oxides may form through natural oxidation of a metal material prior to formation of the resin protective film. However, oxidation progresses further during curing of the resin protective film by heating, resulting in the formation of substantial amounts of metal oxides that become sufficient cause for delamination. Even if complete delamination does not occur, etching of the oxides by the acidic solvent results in interstices forming between the resin protective film and the terminal metal (outer terminals) that are manufactured last. Such interstices cause delamination later and give rise to variation in the electric characteristics of the finished articles, thus impairing reliability.